Process for modifying steel slag through acidification and carbonization coupling

ABSTRACT

The present invention belongs to the technical field of metallurgical solid waste resource utilization, and particularly relates to acidification and carbonization coupling modified steel slag as well as a preparation process and an application thereof. The process specifically includes the following steps of adopting acetic acid, tributyl phosphate, ethanolamine and a NaOH and Ca(OH)2 emulsion as reaction reinforcing agents, and modifying the steel slag together with CO2-rich lime kiln flue gas. The process for modifying the steel slag through acidification and carbonization coupling provided in the present invention has the advantages of simple reaction conditions and no need of high-pressure CO2, additionally, the carbonation reaction rate can be greatly increased, and f-CaO and f-MgO in the steel slag can be effectively eliminated.

TECHNICAL FIELD

The present invention belongs to the technical field of metallurgicalsolid waste resource utilization, and particularly relates toacidification and carbonization coupling modified steel slag as well asa preparation process and an application thereof.

BACKGROUND

The disclosure of the information in the background only aims toincrease understanding of the general background of the presentinvention, but does not need to be deemed to acknowledge or imply in anyform that the information structure has become the well-known prior artto general technicians in the field.

Steel production is one of the main industries emitting CO₂, accordingto the principle of mineral carbonation, steel slag is subjected tocarbonation pretreatment by using CO₂-rich flue gas of a lime kiln, notonly is the carbon sequestration effect achieved, but also theperformance of the steel slag is improved. The direct carbonationreaction of the steel slag is mainly adopted in current research and hasthe following problems: (1) reaction conditions are strict, and a highCO₂ pressure is required; and (2) the carbonation reaction rate is low,f-CaO and f-MgO in the steel slag cannot be effectively eliminatedthrough the carbonation reaction, thus, the carbonation technique of thesteel slag is not popularized or applied, and the comprehensivetreatment problem of the steel slag becomes more and more serious.

SUMMARY

In order to overcome the defects of the prior art, the present inventionprovides acidification and carbonization coupling modified steel slag aswell as a preparation process and an application thereof. On the basisthat the current air quenching treatment process of the steel slag has acontrollable particle size, and the shape of steel slag particles isspherical with smooth surfaces, a new technique is developed, the steelslag is subjected to acidification and carbonization coupling treatment,and various reaction reinforcing agents are added, so that the alkalielimination reaction and the carbonation reaction of f-CaO and f-MgO inthe steel slag are accelerated.

The first aspect of the present invention provides a process formodifying the steel slag through acidification and carbonizationcoupling, and the process specifically includes the following steps ofadopting acetic acid, tributyl phosphate, ethanolamine and a NaOH andCa(OH)₂ emulsion as reaction reinforcing agents, and modifying the steelslag together with CO₂-rich flue gas of a lime kiln.

The second aspect of the present invention provides modified steel slagprepared by adopting the above process.

The third aspect of the present invention provides a device formodifying the steel slag through acidification and carbonizationcoupling, the device includes an acidification and carbonizationcoupling reaction unit, a liquid-solid separation unit and adistillation separation unit, and the acidification and carbonizationcoupling reaction unit, the liquid-solid separation unit and thedistillation separation unit are sequentially connected.

The fourth aspect of the present invention provides an application ofthe modified steel slag to preparing asphalt and concrete aggregates andblending materials for various building materials.

One or more embodiments of the present invention have at least thefollowing beneficial effects:

(1) The process for modifying the steel slag through acidification andcarbonization coupling provided in the present invention has theadvantages of simple reaction conditions and no need of high-pressureCO₂, additionally, the carbonation reaction rate can be greatlyincreased, and f-CaO and f-MgO in the steel slag can be effectivelyeliminated.

(2) A coupling technique of acidification and carbonization couplingpretreatment is adopted to modify steel slag particles, after treatmentis performed by adopting the processing technique, the content of f-CaOcan be reduced to be less than 1.5%, and the volume stability problem iseliminated; and according to different application directions ofproducts, the treatment time and the amount of the reaction reinforcingagents can be adjusted to control the extent of reaction on the surfaceof the steel slag, the hardness of the steel slag particles themselvesis retained, additionally, the problem of bad volume stability caused byf-CaO and f-MgO is eliminated, and therefore, the steel slag can be usedas asphalt and concrete aggregates or concrete aggregates for roads.

At present, limestone and basalt resources are in shortage, the currentprice is about 130 (including tax and freight) yuan per ton, the priceof the steel slag is about 100 yuan per ton (including tax and freight)for accounting, and the benefit of slag per ton is(130−100)*(100%−13%)=26.1 yuan per ton.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings constituting a part of the present inventionare used to provide a further understanding of the present invention.The exemplary embodiments of the present invention and descriptionsthereof are used to explain the present invention, and do not constitutean improper limitation of the present invention.

FIG. 1 is a flow diagram of the process for modifying the steel slagthrough acidification and carbonization coupling and a preparationmethod provided in the present invention.

FIG. 2 is a diagram of the acidification and carbonization coupling unitprovided in the present invention: 1 represents a steel slag feed port,2 represents an exhaust port, 3 represents an acetic acid feed port, 4represents a tributyl phosphate feed port, 5 represents an ethanolaminefeed port, 6 represents a NaOH and Ca(OH)₂ emulsion feed port, 7represents a motor, 8 represents a stirring shaft with spiral blades, 9represents a reaction chamber, 10 represents uniformly distributed limekiln flue gas nozzles and clear water flushing nozzles, 11 represents aPH sensor, 12 represents a temperature sensor, 13 represents a pressuresensor, 14 represents a filter screen with the aperture of 1 mm, 15represents a discharge valve, and 16 represents a three-way valve.

FIG. 3 is a diagram of the liquid-solid separation unit provided in thepresent invention: 1 represents a liquid storage tank, 2 represents aliquid uniform distributor, 3 represents a discharge nozzle and sealingcover, 4 represents filter cloth matched with a vacuum filter, 5represents a suction nozzle matched with the vacuum filter, 6 representsa tail wheel of a conveying belt matched with the vacuum filter, 7represents a head wheel of the conveying belt matched with the vacuumfilter, and 8 represents liquid recycling pipelines and storageequipment.

FIG. 4 is a diagram of the distillation separation unit provided in thepresent invention: 1 represents a distillation chamber, 2 represents aliquid feed port, 3 represents an exhaust port after distillation, 4represents an acetic acid separation chamber, 5 represents an aceticacid feed and storage device, 6 represents an ethanolamine separationchamber, 7 represents an ethanolamine feed and storage device, 8represents a tributyl phosphate separation chamber, 9 represents atributyl phosphate feed and storage device, 10 represents a bottomdrainage and circulation device, and 11 represents condensate waterrecycling equipment.

DETAILED DESCRIPTION

It should be noted that, the following detailed descriptions are allexemplary, and are intended to provide further descriptions of thepresent invention. Unless otherwise specified, all technical andscientific terms used herein have the same meanings as those usuallyunderstood by a person of ordinary skill in the art to which the presentinvention belongs.

It should be noted that the terms used herein are merely used fordescribing specific implementations, and are not intended to limitexemplary implementations of the present invention. As used herein, thesingular form is also intended to include the plural form unless thecontext clearly dictates otherwise. In addition, it should further beunderstood that, terms “comprise” and/or “include” used in thisspecification indicate that there are features, steps, operations,devices, components, and/or combinations thereof.

As introduced in the background, the direct carbonation reaction of thesteel slag is mainly adopted in current research and has the followingproblems: (1) reaction conditions are strict, and a high CO₂ pressure isrequired; and (2) the carbonation reaction rate is low, f-CaO and f-MgOin the steel slag cannot be effectively eliminated through thecarbonation reaction, thus, the carbonation technique of the steel slagis not popularized or applied, and the comprehensive treatment problemof the steel slag becomes more and more serious.

In order to solve the above technical problem, the first aspect of thepresent invention provides a process for modifying steel slag throughacidification and carbonization coupling, and the process specificallyincludes the following steps of adopting acetic acid, tributylphosphate, ethanolamine and a NaOH and Ca(OH)₂ emulsion as reactionreinforcing agents, and processing the steel slag together with CO₂-richflue gas of a lime kiln.

The acetic acid can accelerate the leaching rate of Ca²⁺ and Mg²⁺ inf-CaO and f-MgO in the steel slag; the ethanolamine can increase thesolubility of CO₂ in the lime kiln flue gas (the solubility of CO₂ gasin the ethanolamine is 8.5 times that in a water solution); the tributylphosphate can extract the acetic acid and promote the generation ofCaCO₃, so that the carbonation reaction of the steel slag isaccelerated; and the NaOH and Ca(OH)₂ emulsion is used for adjusting thePH value during carbonation, so that the reaction environment changesfrom acidity to alkalinity, and the carbonation reaction is promoted.The core of the scheme is that an “acidifying technique” is coupled witha “carbonation treatment technique”, the two core processes are mutuallypromoted, the content of f-CaO and f-MgO in the steel slag is reduced,the volume stability problem of the steel slag is solved, and the airquenching treatment process of the steel slag is perfected.

In one or more of implementations of the present invention, the specificsteps include: sequentially adding water and acetic acid solid to steelslag, fully mixing and reacting, then introducing lime kiln flue gascontaining CO₂ gas, and meanwhile, adding tributyl phosphate, a NaOH andCa(OH)₂ emulsion and ethanolamine for acidification and carbonizationcoupling reaction.

Furthermore, the steel slag is preferably air quenched steel slag,because after liquid steel slag is subjected to air quenching treatment,the steel slag particle size is controllable, the average particle sizeis 2 mm, the acidification and carbonization coupling reaction isfacilitated, but the steel slag needs to be subjected to rod millingtreatment after being subjected to hot-smoldering treatment, the averageparticle size is 10 mm, the particle size is large, the reaction rate islow, and the acidification and carbonization coupling reaction is notfacilitated.

Furthermore, when the water and the acetic acid solid are sequentiallyadded to the steel slag, the water amount is controlled according to theliquid-solid ratio of 20:1 to 5:1, and the concentration of acetic acidis controlled to be 5% to 20%.

Furthermore, the mixing reaction time is 20-60 min.

Furthermore, the final total amount of the tributyl phosphate is thesame as the molar mass of the added acetic acid.

Furthermore, the amount of the NaOH and Ca(OH)₂ emulsion is required toadjust the PH value of liquid between 8 and 11.

Furthermore, the total amount of the ethanolamine is 5% to 20%.

Furthermore, the acidification and carbonization coupling reaction timeis controlled to be 15-30 min.

Furthermore, the flue gas pressure is controlled to be 0.1-2 MPa.

Furthermore, the reaction temperature is 25-100° C.

In the acidification and carbonization coupling process, the acetic acidin a solution erodes the surfaces of the steel slag particles andpermeates into the steel slag, Ca²⁺ and Mg²⁺ are leached from f-CaO andf-MgO in the steel slag and a part of Ca in calcium silicate, meanwhile,CO₂ dissolves in water to generate H₂CO₃ which reacts with Ca²⁺ and Mg²⁺to generate CaCO₃ and MgCO₃ so as to promote the reaction, and thereaction formulas are as follows:f-CaO+H₂O→Ca(OH)₂  (1)f-MgO+H₂O→Mg(OH)₂  (2)CaSiO₃+2CH₃COOH→Ca²⁺+2CH₃COO⁻¹+SiO₂+H₂O  (3)Ca²⁺+2CH₃COO⁻¹+CO₂+H₂O→CaCO₃+2CH₃COOH  (4)Mg²⁺+2CH₃COO⁻¹+CO₂+H₂O→MgCO₃+2CH₃COOH  (5)R—NH₂+CO₂+H₂O→R-NH₃ ⁺+HCO₃ ⁻  (6)NaOH+HCO₃ ⁻→Na+CO₃ ²⁻+H₂O  (7)2Ca(OH)₂+2HCO₃ ⁻→2CaCO₃+3H₂O  (8)

The above reaction formulas show that the acidification reaction occursin an acidic environment to eliminate f-CaO and f-MgO in the steel slagand generate calcium acetate, then the calcium acetate reacts withcarbonic acid to generate calcium carbonate and acetic acid, then theacetic acid generated after reaction is extracted with the tributylphosphate as an organic solvent so as to accelerate the carbonationreaction, and it can be seen that the acetic acid is only used as acatalyst in the reaction. But the carbonation reaction and the CO₂dissolution occur in an alkaline environment, therefore, when the aceticacid is extracted with the tributyl phosphate, the ethanolamine whichpromotes the CO₂ dissolution can be added, and the NaOH and Ca(OH)₂emulsion is added in batches to gradually adjust the PH value in theliquid to be 10 to 11 for the carbonation reaction. The adding time andthe contents of the reaction reinforcing agents in the acidification andcarbonization coupling process are controlled, so that the acidificationand carbonization reaction process can be accelerated.

According to the present invention, the acetic acid, the tributylphosphate, the ethanolamine and the NaOH and Ca(OH)₂ emulsion are usedfor performing acidification and carbonization coupling treatment on thesteel slag particles, the treatment time and process are short, most ofalkali in the steel slag can be eliminated, and the f-CaO content can bereduced to be less than 1.5%. The treatment time and the amount of thereaction reinforcing agents and the like can be adjusted according tothe applications of treated products; if the microstructure and theparticle strength of the steel slag particles need to be preferablyretained, process parameters of short treatment time and small amount ofthe reaction reinforcing agents can be selected; and if Ca and Feelements in the steel slag need to be completely separated, thetreatment time is extended, and the amount of the reaction reinforcingagents is increased.

In one or more of implementations of the present invention, after thesteel slag is modified through acidification and carbonization coupling,the modified steel slag is separated from liquid to be treatedseparately, the steel slag is cleaned with circulating water which isdistilled to separate chemical agents, the steel slag is collected, theremaining solid containing suspension continues to be subjected to solidparticle and liquid separation, separated solid is cleaned andcollected, separated liquid is distilled, and obtained components arerecycled.

The remaining solid containing suspension mainly includes CaCO₃, steelslag particles less than 1 mm, acetic acid, tributyl phosphate andethanolamine. The above solid containing suspension continues to besubjected to solid and liquid separation, the remaining liquid includesacetic acid, ethanolamine and tributyl phosphate, the boiling point ofthe acetic acid is 117.9° C., the boiling point of the ethanolamine is170.9° C., the boiling point of the tributyl phosphate is 288.28° C.,therefore, according to different boiling points of three chemicalsubstances, the three chemical substances can be separated by using adistillation separation column and then are recycled, the treatment costof the technique is reduced, and the problem of environmental pollutionis solved.

The second aspect of the present invention provides modified steel slagprepared by adopting the above process.

The third aspect of the present invention provides a device formodifying steel slag through acidification and carbonization coupling,the device includes an acidification and carbonization coupling reactionunit, a liquid-solid separation unit and a distillation separation unit,and the acidification and carbonization coupling reaction unit, theliquid-solid separation unit and the distillation separation unit aresequentially connected.

The steel slag particles pass through the liquid-solid separation unitto separate liquid and solid after being treated by the acidificationand carbonization coupling reaction unit, the solid is conveyed to astorage yard for storage and standby application after being cleaned,the liquid passes through the distillation separation unit to separateacetic acid, tributyl phosphate, ethanolamine and return condensatewater, waste water generated in all links of the process is treated andrecycled, and substances harmful to the environment are not dischargedin the process.

In one or more of implementations of the present invention, theacidification and carbonization coupling reaction unit includes areaction chamber, a steel slag feed port, an exhaust port and a motorare formed in and arranged on the upper end of the reaction chamber, andan acetic acid feed port, a tributyl phosphate feed port, anethanolamine feed port and a NaOH and Ca(OH)₂ emulsion feed port arefurther formed in the upper end of the reaction chamber.

Furthermore, the motor is connected with a stirring shaft with spiralblades, and the spiral blades are driven to rotate by virtue of thestirring shaft, so that materials in the reaction chamber are uniformlymixed.

Furthermore, uniformly distributed lime kiln flue gas nozzles and clearwater flushing nozzles are arranged on the side surface of the reactionchamber.

Furthermore, a temperature sensor and a pressure sensor are arrangedabove the lime kiln flue gas nozzles and the clear water flushingnozzles.

Furthermore, a pressure sensor is arranged near the exhaust port.

Furthermore, a filter screen with the aperture of 1 mm is arranged atthe bottom of the reaction chamber.

Furthermore, a discharge valve is arranged below the filter screen, athree-way valve is equipped below the discharge valve, and the three-wayvalve respectively communicates with the reaction chamber, a solidchannel and a liquid channel.

Furthermore, the body structure of the acidification and carbonizationcoupling reaction unit is made of stainless steel, and a wear-resistinglining plate is attached to the position, which makes contact with thesteel slag, of the interior of the reaction chamber.

After the acidification and carbonization coupling reaction is finished,first, most of liquid in the reaction unit is filtered through thefilter screen and is discharged into the liquid storage tank through theliquid channel, i.e. the solid containing suspension; and then the steelslag is flushed with clear water in the clear water flushing nozzles,chemical agents attached to the steel slag particles are washed out, andliquid enters the storage tank. Then the three-way valve is turned tothe other side, a filter screen valve at the bottom of the reactionchamber is opened, and the steel slag falls into the solid channel andis conveyed to the storage yard for standby application through a belt.

In one or more of implementations of the present invention, theliquid-solid separation unit includes a liquid storage tank, a liquiduniform distributor, a discharge nozzle and sealing cover, a vacuumfilter and a liquid recycling pipeline.

The solid containing suspension which is treated by the acidificationand carbonization coupling reaction unit is stored in the liquid storagetank, is pretreated through the liquid uniform distributor and thenenters the vacuum filter to be filtered through the discharge nozzle, sothat solid-liquid separation is achieved, separated liquid is collectedfrom the liquid recycling pipeline, the liquid collected from the liquidrecycling pipeline is pumped into the liquid storage tank of thedistillation separation unit for standby application, and solid isconveyed to the storage yard for standby application.

In one or more of implementations of the present invention, thedistillation separation unit includes a distillation chamber, and aliquid feed port and an exhaust port are formed in the upper end of thedistillation chamber; and an acetic acid separation chamber, anethanolamine separation chamber and a tributyl phosphate separationchamber are sequentially arranged in the distillation chamber from topto bottom, and corresponding liquid storage devices are respectivelyarranged at the bottoms of the separation chambers and are used fordirectly feeding the acetic acid feed port, the tributyl phosphate feedport and the ethanolamine feed port of the acidification andcarbonization coupling reaction unit.

The acetic acid separation chamber, the ethanolamine separation chamberand the tributyl phosphate separation chamber are separated andcommunicate with each other through pipelines.

The exhaust port is connected with condensate water recycling equipment,and recycled condensate water is used for cleaning steel slag and theacidification and carbonization coupling reaction.

A drainage and circulation device is arranged at the bottom of thedistillation chamber and communicates with a feed device of thedistillation separation column.

Steam is used as a heat source in the distillation process, the steam isgenerated by a waste heat boiler in the steel slag treatment process, oris generated by a waste heat boiler of a lime rotary kiln or isgenerated in other process links, and the steam temperature is requiredto be higher than or equal to 350° C.

The fourth aspect of the present invention provides an application ofthe modified steel slag to preparing asphalt and concrete aggregates andblending materials for various building materials.

In order to enable those skilled in the art to understand the technicalsolutions of the present invention more clearly, the technical solutionsof the present invention will be described in detail below withreference to specific embodiments.

A process for modifying steel slag through acidification andcarbonization coupling:

Steel slag particles enter an acidification and carbonization couplingreaction unit through a belt or a bucket conveyor, first, water isadded, a spiral stirrer is started, then acetic acid solid is added, theconcentration of acetic acid is controlled to be 5% to 20% and isadjusted according to the contents of particles and f-CaO ofto-be-treated steel slag, the steel slag is continuously added inbatches, and the reaction time is controlled to be 20-60 min. The PHvalue of liquid in a tank is measured by using a PH measuring instrumentinserted into a reactor, then lime kiln flue gas containing CO₂ gas isintroduced, tributyl phosphate is added in batches, and the final totalamount is the same as the molar mass of the acetic acid. A NaOH andCa(OH)₂ emulsion is added, the PH value of the liquid is adjustedbetween 8 and 11, ethanolamine is added in batches, the solubility ofthe CO₂ gas in the ethanolamine is 8.5 times that in a water solution,therefore, the solubility of the CO₂ gas is increased by adding theethanolamine, the carbonation reaction is intensified, the total amountof the ethanolamine is controlled to be 5% to 20%, the carbonationreaction occurs, the time is controlled to be 15-30 min, the gaspressure in the tank is controlled to be 0.1-2 MPa, the reactiontemperature is 25-100° C., after the set reaction time is reached, amatched fan in the reaction unit is turned on to exhaust, the liquid inthe reaction unit is discharged, the steel slag is cleaned withcirculating water distilled to separate chemical agents, and the steelslag is discharged to a storage yard for standby application.

A solid containing suspension enters a liquid-solid separation unit,solid particles are separated from liquid through vacuum filterequipment, separated solid is cleaned through nozzles on the upper partof the filter, and liquid enters the storage tank and a distillationseparation unit.

The liquid is conveyed to a feed device of the distillation separationunit through a pump and a pipeline, steam which is generated by a wasteheat boiler in the steel slag treatment process, or is generated by atail gas waste heat boiler of a lime kiln or is generated by othersources is used, the steam temperature is required to be higher than orequal to 350° C., the boiling point of the acetic acid is 117.9° C., theboiling point of the ethanolamine is 170.9° C., the boiling point of thetributyl phosphate is 288.28° C., according to different boiling pointsof three chemical substances, the three chemical substances areseparated by a distillation separation column and then are recycled, thetreatment cost of the technique is reduced, the problem of environmentalpollution is solved, and water is recycled through condensate waterrecycling device for cyclic utilization.

Further description is given below with reference to the specificaccompanying drawings:

Embodiment 1

A process for modifying steel slag through acidification andcarbonization coupling:

(1) Steel slag particles are conveyed to enter an acidification andcarbonization coupling reaction unit, and equipment numbers are shown inFIG. 2 . The steel slag particles enter a reaction chamber 9 through asteel slag feed port 1, circulating water is added to the reaction unitthrough a NaOH and Ca(OH)₂ emulsion feed port 6, the liquid-solid ratiois set to 5:1, the water amount is controlled, a motor 7 is started todrive a stirring shaft 8 with spiral blades to move, acetic acid solidis added in batches through an acetic acid feed port 3, mixing andreaction are performed for 20 min, then tributyl phosphate is addedthrough a tributyl phosphate feed port 4, meanwhile, lime kiln flue gascontaining CO₂ is sprayed through lime kiln flue gas nozzles 10, theflue gas pressure is controlled to be 0.1 MPa, ethanolamine (5%) isadded in batches through an ethanolamine feed port 5, the solubility ofCO₂ is increased, a NaOH and Ca(OH)₂ emulsion is added through a NaOHand Ca(OH)₂ emulsion feed port 6, the PH value of the carbonationreaction is adjusted, after the reaction is finished, filtering througha filter screen 14 is performed, a discharge valve 15 and a three-wayvalve 16 are opened, the steel slag particles of 1 mm are separated froma solid containing suspension, and when water is drained, steel slag iscleaned with clean circulating water in the reaction chamber and then isconveyed to a storage yard for standby application.

(2) As shown in FIG. 3 , the solid containing suspension enters a liquidstorage tank 1 of a liquid-solid separation unit, the solid containingsuspension is uniformly shunted and distributed through a liquid uniformdistributor 2 and a discharge nozzle 3 and then enters a vacuum filter,liquid uniformly falls onto filter cloth 4 matched with the vacuumfilter, solid and liquid with a low solid content are separated throughvacuum suction of a suction nozzle 5, the solid is further cleanedthrough cleaning nozzles arranged in the discharge nozzle 3 and then isconveyed to the storage yard for standby application through a tailwheel 6 and a head wheel 7, and the liquid is conveyed into the storagetank after being collected through a liquid recycling pipeline 8 andenters a distillation separation unit.

(3) As shown in FIG. 4 , the liquid enters a distillation chamber 1 ofthe distillation separation unit through a feed port 2, an acetic acidseparation chamber 4, an ethanolamine separation chamber 6 and atributyl phosphate separation chamber 8 are heated by using steam, thetemperatures are respectively controlled to be 288.28° C., 170.9° C. and117.9° C., collection is performed through an acetic acid feed andstorage device 5, an ethanolamine feed and storage device 7 and atributyl phosphate feed and storage device 9, tributyl phosphate,ethanolamine and acetic acid are separated and separately collected, theremaining water-rich steam enters condensate water recycling equipment11 through an exhaust port 3, and recycled condensate water from thesteam is 100% recycled without discharge or pollution.

Embodiment 2

A process for modifying steel slag through acidification andcarbonization coupling:

(1) Steel slag particles are conveyed to enter an acidification andcarbonization coupling reaction unit, and equipment numbers are shown inFIG. 2 . The steel slag particles enters a reaction chamber 9 through asteel slag feed port 1, circulating water is added to the reaction unitthrough a NaOH and Ca(OH)₂ emulsion feed port 6, the liquid-solid ratiois set to 20:1, the water amount is controlled, a motor 7 is started todrive a stirring shaft 8 with spiral blades to move, acetic acid solidis added in batches through an acetic acid feed port 3, mixing andreaction are performed for 60 min, then tributyl phosphate is addedthrough a tributyl phosphate feed port 4, meanwhile, lime kiln flue gascontaining CO₂ is sprayed through lime kiln flue gas nozzles 10, theflue gas pressure is controlled to be 2 MPa, ethanolamine (20%) is addedin batches through an ethanolamine feed port 5, the solubility of CO₂ isincreased, a NaOH and Ca(OH)₂ emulsion is added through a NaOH andCa(OH)₂ emulsion feed port 6, the PH value of the carbonation reactionis adjusted, after the reaction is finished, filtering through a filterscreen 14 is performed, a discharge valve 15 and a three-way valve 16are opened, the steel slag particles of 1 mm are separated from a solidcontaining suspension, and when water is drained, steel slag is cleanedwith clean circulating water in the reaction chamber and then isconveyed to a storage yard for standby application.

(2) As shown in FIG. 3 , the solid containing suspension enters a liquidstorage tank 1 of a liquid-solid separation unit, the solid containingsuspension is uniformly shunted and distributed through a liquid uniformdistributor 2 and a discharge nozzle 3 and then enters a vacuum filter,liquid uniformly falls onto filter cloth 4 matched with the vacuumfilter, solid and liquid with a low solid content are separated throughvacuum suction of a suction nozzle 5, the solid is further cleanedthrough cleaning nozzles arranged in the discharge nozzle 3 and then isconveyed to the storage yard for standby application through a tailwheel 6 and a head wheel 7, and the liquid is conveyed into the storagetank after being collected through a liquid recycling pipeline 8 andenters a distillation separation unit.

(3) As shown in FIG. 4 , the liquid enters a distillation chamber 1 ofthe distillation separation unit through a feed port 2, an acetic acidseparation chamber 4, an ethanolamine separation chamber 6 and atributyl phosphate separation chamber 8 are heated by using steam, thetemperatures are respectively controlled to be 288.28° C., 170.9° C. and117.9° C., collection is performed through an acetic acid feed andstorage device 5, an ethanolamine feed and storage device 7 and atributyl phosphate feed and storage device 9, tributyl phosphate,ethanolamine and acetic acid are separated and separately collected, theremaining water-rich steam enters condensate water recycling equipment11 through an exhaust port 3, and recycled condensate water from thesteam is 100% recycled without discharge or pollution.

The foregoing descriptions are merely preferred embodiments of thepresent invention and are not intended to limit the present invention. Aperson skilled in the art may make various alterations and variations tothe present invention. Any modification, equivalent replacement, orimprovement made within the spirit and principle of the presentinvention shall fall within the protection scope of the presentinvention.

What is claimed is:
 1. A process for modifying steel slag throughacidification and carbonization coupling, wherein acetic acid, tributylphosphate, ethanolamine and a NaOH and Ca(OH)₂ emulsion are used asreaction reinforcing agents, and the steel slag is modified togetherwith CO₂-rich lime kiln flue gas; the process for modifying the steelslag through acidification and carbonization coupling specificallycomprises the steps of sequentially adding water and acetic acid solidto the steel slag, mixing and reacting for 20-60 min, then introducingthe lime kiln flue gas containing CO₂ gas, and meanwhile, and adding thetributyl phosphate, the NaOH and Ca(OH)₂ emulsion and the ethanolaminefor acidification and carbonization coupling reaction; when the waterand the acetic acid solid are sequentially added to the steel slag, thewater amount is controlled according to the liquid-solid ratio of 20:1to 5:1, and the concentration of the acetic acid is controlled to be 5%to 20%; the final total amount of the tributyl phosphate is the same asthe molar mass of the added acetic acid; the amount of the NaOH andCa(OH)₂ emulsion is required to adjust the pH value of liquid between 8and 11; and the amount of the ethanolamine is 5% to 20%.
 2. The processfor modifying the steel slag through acidification and carbonizationcoupling according to claim 1, wherein the acidification andcarbonization coupling reaction time is controlled to be 15-30 min. 3.The process for modifying the steel slag through acidification andcarbonization coupling according to claim 1, wherein the flue gaspressure is controlled to be 0.1-2 MPa.
 4. The process for modifying thesteel slag through acidification and carbonization coupling according toclaim 1, wherein the reaction temperature is 25-100° C.